Oral Presentation Australian Society for Microbiology Annual Scientific Meeting 2014

Effects of arabinoxylan dietary fibre fine structure on gut microbiota dynamics. (#34)

Deirdre Mikkelsen 1 2 , Barbara A Williams 1 2 , Scott Godwin 3 , Lisa-Maree Gulino 2 3 , Diane Ouwerkerk 2 3 , Munirah Ismail 1 , Athol Klieve 2 3 4 , Michael J Gidley 1 2
  1. ARC Centre of Excellence in Plant Cell Walls, Centre for Nutrition and Food Sciences, University of Queensland, Brisbane, QLD, Australia
  2. Queensland Alliance for Agriculture and Food Innovation, University of Queensland, Brisbane, QLD, Australia
  3. Rumen Ecology Unit, Agri-Science Queensland , Department of Agriculture, Fisheries and Forestry, Brisbane, QLD, Australia
  4. School of Agriculture and Food Sciences, University of Queensland, Gatton, QLD, Australia

It is widely accepted that a substantial proportion of the energy in a healthy human diet should come from whole grains, fruits and vegetables. The dietary fibre content of these consumed foods is now recognised to be associated with alleviation of diseases such as type II diabetes, colorectal cancer and cardiovascular diseases.

Wheat is a staple of the Australian diet, and the major dietary fibre component of this grain is arabinoxylan (AX). The chemical structure comprises a polymeric xylose (Xyl) backbone, with individual xylose units either un-substituted, or mono- or di-substituted with arabinose (Ara) residues. These structural features affect the physico-chemical properties of AX, and subsequently its interactions with other plant cell wall constituents. In plants, AX arabinofuranohydrolases (AXAHs) alter the amount of AX substitution during grain development. In humans, specific resident gastro-intestinal bacteria produce α-L-arabinofuranosidases. These bacterial enzymes are equivalents to AXAHs, sharing similar modes of action, and may alter AX fine structure by depleting Ara residues from the Xyl backbone, thus affecting host nutritional benefits.

The fermentability of enzymatically modified AX with bacterial α-L-arabinofuranosidases, causing depletion in mono- or di-substituted Ara residues, or both, was assessed by in vitro batch culture, using pig faecal inoculum as a model for humans. Wheat and rye AX varying in their Ara:Xyl ratios, and substitution patterns were used as controls. During fermentation, cumulative gas production was measured at regular intervals as an indicator of the reaction kinetics, and short chain fatty acid end-products were analysed. Significant differences were observed between substrates varying in their Ara:Xyl ratios, for all fermentability parameters. The effects of arabinose depletion on AX-gut microbe interactions were assessed using 454-amplicon pyrosequencing, specifically examining the V3/V4 region of the 16S rRNA gene. Adopting such an experimental approach will elucidate the prebiotic health benefits of dietary fibre within the complex gut ecosystem.